During the operation of such a vehicle air conditioning system, in particular during the cooling mode, during which the evaporator is cooled, water condenses in the evaporator from the air to be fed to the interior of the vehicle and blown through the evaporator by means of the fan, in particular if the air is warm and/or moist. The condensed water collects in the evaporator, for example on the surfaces of cold pipes, plates and/or cooling fins. If the quantity of the condensed water in the evaporator has reached a certain quantity, condensed water is discharged from the evaporator to the exterior in a known manner.
However, a residual amount of condensed water remaining in the evaporator following the cooling mode of the vehicle air conditioning system cannot generally be prevented, for example as a result of surface tension. However, the result of said residual quantity of water in the evaporator can, if following the cooling mode the vehicle air conditioning system is only operated in the ventilation mode, in which the evaporator is not cooled and the air to be fed to the interior of the vehicle is blown through the warming evaporator by means of the fan, be that the condensed water collected in the evaporator is suddenly evaporated and is carried with the air flow into the interior of the vehicle, where it can condense on (cold) vehicle window panes, which is referred to here as “flash fogging”. The misting of the window panes results in significantly restricted vision through the same. In order to prevent the flash-fogging effect, the evaporator must be kept cool and hence the vehicle air conditioning system must be operated in the cooling mode. However, the cooling mode of the vehicle air conditioning system requires significantly more energy in comparison to the pure ventilation mode and should only be used to prevent the misting of the window panes or to provide a pleasant climate in relation to temperature and air humidity for the vehicle occupants in the interior of the vehicle.
A generic vehicle air conditioning system is known from DE 102 27 660 B3 for example, with which the flash-fogging effect is prevented by the controlled evaporation of condensed water deposited on the evaporator during a drying phase. For this a control device of the vehicle air conditioning system is configured to control the amount of thermal energy that is fed to the evaporator during the drying phase per unit time accordingly.
Against this background, the object of the present invention is to provide a method for operating a vehicle air conditioning system as well as a vehicle air conditioning system, with which the flash-fogging effect can be reliably prevented inexpensively. Moreover, the method as well as the air conditioning system should also contribute to a saving of energy when operating the air conditioning system.